The metabolic syndrome is a cluster of disorders that includes obesity, dyslipidemia, hypertension, non- alcoholic fatty liver disease and insulin resistance, all of which predispose to the development of diabetes and cardiovascular disease. Epidemiological and clinical data indicate that increased sugar, and particularly fructose, ingestion is a major contributor to the development of the metabolic syndrome and progression to diabetes. The mechanisms by which fructose consumption causes metabolic dysfunction remain elusive. Carbohydrate Responsive-Element Binding Protein (ChREBP) is a master transcriptional regulator of glycolytic and lipogenic gene programs which is activated by products of carbohydrate metabolism. SNPs in the ChREBP locus identified in genome-wide association studies predict features of the metabolic syndrome in human populations. We recently discovered a novel, potent constitutively active isoform of ChREBP, ChREBP-beta. In vivo, ChREBP-beta expression is acutely and robustly increased by fructose ingestion, but only modestly by glucose ingestion. Mice with whole-body genetic deletion of ChREBP die within several days of high-fructose feeding. In this proposal, we will pursue an integrative physiological approach to determine the role of ChREBP in fructose-induced metabolic disturbances. We hypothesize that ChREBP, and particularly ChREBP-beta, is a key regulatory element that is required for the normal adaptive metabolic response to fructose ingestion and also contributes to the development of metabolic disease and diabetes when sugar is consumed in excess. Using a combination of genetic and dietary interventions in mouse models, we will evaluate the role of ChREBP in integrated fuel homeostasis by pursuing the following three aims. In Aim 1, using tissue-specific, loss-of-function mouse models, we will explore the physiologic and cellular mechanisms by which the absence of ChREBP impairs integrated fuel homeostasis and causes fructose intolerance. In Aim 2, using a ChREBP gain-of-function mouse model combined with diets of different carbohydrate content and composition, we will explore a novel concept that the effects of ChREBP activity on integrated fuel homeostasis and insulin sensitivity depend on the nutritional context. In Aim 3, we will develop a novel, ChREBP-beta isoform specific conditional loss-of-function mouse model to begin to determine the physiological significance of the distinct ChREBP isoforms in relation to integrated fuel metabolism and fructose induced metabolic disease. We anticipate that these studies will provide fundamental insight into mechanisms of fructose-induced metabolic disease and lay the groundwork for novel strategies for the prevention and treatment of obesity and diabetes.